Frequency modification techniques that adjust an operating frequency to compensate for aging electronic components

ABSTRACT

A number of performance parameters for the electronic system are determined at a particular age of the electronic system. The performance parameters can be correlated to maximum operating frequency of electronic components of the electronic system for the particular age of the electronic system. Operating frequency of the electronic components is adjusted in accordance with the performance parameters. The performance parameters may be predetermined (such as through reliability and burn-in testing), determined during the life of the electronic system, or some combination of these. Performance parameters can comprise prior operating frequencies, hours of operation, ambient temperature, and supply voltage. Performance parameters can comprise performance statistics determined using age-monitoring circuits, where an aged circuit is compared with a circuit enabled only for comparison. Performance statistics may also be determined though error detection circuits. If an error is detected, the operating frequency can be reduced.

FIELD OF THE INVENTION

The present invention relates to electronic systems and, moreparticularly, relates to frequency regulation for electronic componentsof the electronic systems.

BACKGROUND OF THE INVENTION

Modern electronic systems, such as computers, contain clock generationcircuits that generate one or more frequencies at which electroniccomponents in the system operate. Electronic systems are tested toguarantee system reliability at a given operating frequency. One typicalreliability test is called wear-out acceleration. As is known in theart, wear-out acceleration is used to accelerate the aging of electronicsystems in order to determine possible mechanisms that cause failure orreduced reliability as electronic systems age. Wear-out accelerationoperates components beyond their specified operating range, forinstance, at one and a half times their nominal voltage and at elevatedtemperatures for a specified time period, typically hours or daysinstead of years.

Information from wear-out acceleration is used to adjust such things asfrequency of operation of the electronic system. A low frequency ischosen based on the wear-out acceleration information so that theelectronic system will operate correctly when the system has been aged.Frequency of operation of an electronic system therefore has a “guardband” used to ensure proper operation over the life of the electronicsystem.

There is a need to provide techniques for modifying the frequency ofelectronic systems as the systems age to minimize the guard band andoperate a system at near peak performance over its entire lifetime.

SUMMARY OF THE INVENTION

Exemplary aspects of the present invention provide frequencymodification techniques that adjust an operating frequency of anelectronic system to compensate for one or more aging electroniccomponents. In general, exemplary aspects of the present invention willvary the operating frequency over the life of the electronic system.

One or more performance parameters for the electronic system aredetermined for a particular age of the electronic system. Theperformance parameters can be correlated to maximum operating frequencyof the electronic system for the particular age of the electronicsystem. The operating frequency of electronic components of theelectronic system is adjusted in accordance with the performanceparameters.

The operating frequency of the electronic system may be adjustedaccording to a predetermined schedule (e.g. determined before theelectronic system is first operated), adjusted dynamically during thelife of the electronic system, or adjusted by some combination of these.In all cases, one or more performance parameters influence the choice ofan adjustment to operating frequency for a particular age of theelectronic system.

A more complete understanding of the present invention, as well asfurther features and advantages of the present invention, will beobtained by reference to the following detailed description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exemplary graph of the performance parameter of maximumsystem operating frequency (in this example, maximum system clockfrequency) versus hours of operation, in accordance with an aspect ofpresent invention;

FIG. 1B is an exemplary table showing hours of operation and modifiedoperating frequencies (in this example, maximum system clock frequency),in accordance with a first and a second embodiment of the presentinvention;

FIG. 2 is an exemplary flow chart of a method for scheduled modificationof operating frequency, in accordance with the first and the secondembodiment of the present invention;

FIG. 3 is an exemplary system implementing the method of FIG. 2, inaccordance with the first and the second embodiment of the presentinvention;

FIG. 4 is an exemplary flow chart of a method using the performanceparameter of determined performance in order to modify operatingfrequency, in accordance with a third embodiment of the presentinvention;

FIG. 5 is an exemplary system implementing the methods of FIG. 4 andFIG. 6, in accordance with the third and a fourth embodiment,respectively, of the present invention; and

FIG. 6 is an exemplary flow chart of a method using the performanceparameter of error determination in order to modify operating frequency,in accordance with the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A variety of mechanisms cause electronic component failure over time.One such mechanism is the “hot carrier” effect. Hot carriers are highenergy electrons or holes that, in part, compose thesource-to-drain-electron current traversing a channel underlying a gateof a field effect transistor (FET). For example, hot electrons in anN-type FET (NFET), which uses electrons as carriers, have enough energyto surmount the energy barrier of a portion of the gate insulator. Overtime, some of the hot electrons get trapped in the gate insulator. Thepresence of the electric field effectively increases the NFET thresholdvoltage, thereby making the NFET less conductive as more of theelectrons collect in the gate insulator over time. This wear-out effectmay cause a system failure when transistor speed is reduced sufficientlyenough that signals cannot be generated at the rate of the system clock.

Wear-out effects mean that electronic components are no longer are ableto operate at the speed to which the electronic components were capableof originally. Electronic systems are therefore, as describedpreviously, designed with a “guard band” that enables proper operationfor an aged system, and unfortunately this guard band reduces themaximum performance of a new system.

Thus, the maximum operating frequency of an electronic system usuallydeteriorates over its lifetime due to many wear-out phenomena.Presently, a fixed frequency is imposed on the system for its entirelifetime, excluding the techniques of voltage and frequency scaling forpower management, as known in the art. The fixed frequency includes aguard band to account for the aging of its most sensitive components.The initial frequency of an electronic system may be increased if thesystem frequency could later be reduced to accommodate the effects ofaging.

Exemplary aspects of the present invention use performance parameters ofan electronic system in order to gauge how quickly the system ages and,with this knowledge, adjust the operating frequency at which theelectronic system or electronic components thereof should operate.Examples of performance parameters may include prior operatingfrequencies, predetermined operating frequencies, total hours ofoperation, operating voltages, and operating temperatures. Performanceparameters may also include a multiplicand of a base frequency, such as“1.0” or “0.9,” that, when multiplied with the base frequency, yieldsthe predetermined operating frequency.

In exemplary aspects of the present invention, techniques are proposedfor modifying the operating frequency of an electronic system, theoperating frequency of some of its electronic components, or theoperating frequency of all of its electronic components. A system inaccordance with certain embodiments of the present invention wouldinitially offer higher performance than conventional systems provide,and then as the effects of aging manifest themselves, the performance ofthe system would be incrementally reduced by incrementally adjusting itsfrequency until it reached the level of performance available in today'ssystems that is the performance specified for end-of-life. After eachincremental reduction in frequency, it might be necessary to reduce theworkload of the system and to redirect it to other systems to preventcongestion. Given that hardware prices fall precipitously each year as aresult of sharper photolithography and rapidly improving manufacturingmethods, the total cost of additional capacity would be minimal.

A performance parameter may include, e.g., total hours of operation, aprior operating frequency, predetermined operating frequency, operatingvoltage, or ambient temperature of the electronic system. A performanceparameter may similarly be a multiplicand that, when multiplied with abase frequency, is the equivalent of the predetermined operatingfrequency. The multiplicand may vary over time, just as thepredetermined operating frequency is expected to vary over time.

Maximum operating frequency is generally considered the frequency abovewhich errors will occur during operation of the electronic system or itselectronic components. An indirect method for determining maximumfrequency would involve measuring the switching speed of a test circuitlocated within the same chip or package as the system or its component.In contrast, a direct method for determining maximum frequency wouldinvolve running system at frequencies at or above maximum frequency.Error checking circuits embedded within the actual logic circuits of theelectronic component would detect when the operating frequency hadexceeded the maximum frequency.

The correlation between maximum operating frequency and performanceparameters may be determined through reliability testing, such aswear-out acceleration. Such testing generally entails placing highersupply voltages and ambient temperatures on samples of the electronicsystem. The samples are then “aged” and information can be determinedabout how the maximum operating frequency of the electronic system orelectronic components thereon should be changed over the life of asubstantially equivalent electronic system. Predetermined operatingfrequencies and corresponding performance parameters may be pre-loadedinto the electronic system prior to its sale. The performance parameterin this situation may be total hours of operation. The predeterminedoperating frequencies may be the maximum operating frequencies forcorresponding hours of operation. In general, however, the predeterminedoperating frequencies will be set less than the maximum operatingfrequencies. When the electronic system meets a particular age, definedby the total hours of operation, a corresponding predetermined operatingfrequency is used as the operating frequency for the electroniccomponents.

Performance parameters may also be dynamically determined as the systemages, such as through performance statistics gathered from feedbackcircuits. The feedback circuits measure performance of the electronicsystem though various techniques. For instance, feedback circuits may beage-monitoring circuits, where an aged circuit is compared with acircuit enabled only for comparison. The circuit enabled only forcomparison is called a “new” circuit. Performance statistics for the twocircuits can then be used to adjust operating frequency for electroniccomponents of the electronic system. Additionally, feedback circuits maybe error detecting circuits. When an error occurs, the operatingfrequency can be lowered from a current operating frequency. Executioncan be caused to begin at a point before the error occurred, and then itcan be determined if the error reoccurs. If the error does not reoccur,the lowered operating frequency serves as the new operating frequency.

Additionally, through networks or other links, near maximum operatingfrequencies and corresponding performance parameters could be loadedinto an electronic system while it was operating in the field. Forinstance, a company could determine through testing of an electronicsystem in its laboratory that a similar electronic system in the fieldshould run at certain operating frequencies when the electronic systemreaches particular age milestones.

In this invention, multiple techniques are proposed to control theoperating frequency of a system in order to control the performance ofan electronic system over its entire life cycle. In a first exemplaryembodiment, a control unit is described that would propagate scheduledfrequency reductions, based on prior reliability testing. Frequencyreductions in a second exemplary embodiment could be disseminatedthrough a network as data are gathered and updated from hardwaremeasurements taken on a test system or systems located in a companylaboratory or on other similar electronic systems located elsewhere. Ina third exemplary embodiment, a control unit is proposed that wouldreduce the frequency of the system based on feedback gathered fromage-monitoring circuits. In a fourth exemplary embodiment, a controlunit is proposed that would reduce the frequency of the system upondetection of an error and reset the instruction queue of the system to astate before the error occurred so that the error would be nullified.

To relate a maximum operating frequency of a system to an age of thesystem, it is useful to consider hardware measurements and circuitanalysis. An age of the system can be measured through, for instance,hours, days, or years of operation of the electronic system. Hardwaremeasurements can provide calibration statistics to improve the accuracyof the circuit analysis. To reduce analysis time, electronic systems maybe subjected to operating conditions that accelerate aging and wear-out,such as higher voltages (e.g., one-and-one-half times that of themaximum voltage provided in the specification for the electronic system)and higher temperatures (e.g., 140 degrees Celsius instead of 100degrees Celsius typically provided in the specification for theelectronic system), as is well known to those familiar with the art ofreliability testing. These results can then be used to develop arelationship between operating frequency and performance parameters. Aspreviously described, examples of such performance parameters include,but are not restricted to, prior operating frequency, temperature,supply voltage, and hours of operation. From this relationship, a table(e.g., a “wear-out” table) of values may be created and stored so thatthe operating frequency of a system may be adjusted at periodicintervals to compensate for the effects of aging. The values includepredetermined operating frequencies and corresponding hours ofoperation. Adjustments to the operating frequency may be made based onassessment of performance parameters gathered before an electronicsystem is put into use (according to the first exemplary embodiment ofthe invention), after the electronic system is put into use (accordingto the second exemplary embodiment of the invention), or a combinationof the two.

FIG. 1A depicts a graph comparing the maximum system operating frequency(in this example, maximum system clock frequency) to hours of operation,and

FIG. 1B depicts a wear-out table, extracted from the graph in FIG. 1A,that tabulates the frequency deterioration for discrete time intervals.Curve 4 relates every hour of operation to a maximum operatingfrequency. The information in FIGS. 1A and 1B are determined fromreliability testing.

As previously described, it is possible to determine from reliabilitytesting how an electronic system, and its constituent electroniccomponents, perform over their lifetimes. This type of information canbe used to form a table, such as shown in FIG. 1B, that an electronicsystem will use, in part, to govern its operating frequency as it ages.The table may include maximum operating frequencies for selected ages ofthe electronic system.

As stated above, maximum operating frequency is generally considered thefrequency above which errors will occur during operation of theelectronic system or its electronic components. As used herein,“operating frequency” is generally synonymous to “clock frequency,” andis the frequency supplied to the electronic components. However, itshould be noted that a clock (usually having an “oscillator”) may haveits output multiplied in order to create an operating frequency. In theexamples of FIGS. 1A and 1B, it is assumed that the operating frequencyand clock frequency are the same (e.g., such that all electroniccomponents on the electronic system have the same input frequency of theclock frequency), although as shown below, this does not have to be thecase.

In the example of FIG. 1A, maximum operating clock frequency falls asthe system ages. Segment 5 represents initial operation (e.g., zerohours of operation). The point where curve 4 intersects segment 5 is amaximum operating clock frequency at which a new system can reliablyoperate. Segment 6 represents a time after “A” hours of systemoperation, and the point where it intersects curve 4 is the maximumclock frequency after “A” hours of operation. Segment 7 represents hoursof operation at the end-of-life of the system. In the absence of amethod for adjusting system performance, such as that described herein,the system operating frequency would initially have to be set to theend-of-life frequency at the intersection of curve 4 and segment 7. Themethod described herein allows the system clock frequency to be setinitially to a higher value, the point where curve 4 and segment 6intersect or slightly lower than the frequency at this point. Thisintersection will be designated as F1. F1 will be stored as apredetermined operating frequency for the time period between segments 5and 6. A predetermined operating frequency is preferably as close tomaximum operating frequency as possible, but will generally be set lessthan the maximum operating frequency.

A wear-out table 9, such as the table shown in FIG. 1B, may be generatedfrom curve 4. Table 9 relates a set of hours of operation to a set ofpredetermined operating frequencies at which the system will properlyoperate. Frequency F1, which was determined from information previouslydescribed and shown in FIG. 1A, is entered in the first data row oftable 9, and relates that frequency to the number of hours of operationthat the system may reliably operate at frequency F1. Likewise, theremaining data rows of the example table relate other predeterminedsystem operating frequencies to hours of operation over the lifetime ofthe system.

Although FIG. 1A shows a linear relationship between hours of operationand maximum system clock frequency, the relationship need not be linear.

In a first exemplary embodiment, a control unit propagates scheduledfrequency reductions in productivity through a system clock. The method200 depicted in FIG. 2 describes how the wear-out table 9, shown in FIG.1B, may be used in a processing system depicted in FIG. 3 to controlsystem operating frequencies throughout the lifetime of a system. In theflow chart 200 of FIG. 2, the current hours of operation (e.g., dates)are periodically compared to the hours (e.g., dates) listed in awear-out schedule (step 201), which has, for instance, an adjustment logand a fixed wear-out table. An adjustment is needed when the currentdate exceeds the next incremental date entry, defined as the date entryin the fixed wear-out table that immediately follows the date entrypresently stored in the adjustment log. If an adjustment is needed (step202=YES), frequency adjustment values are loaded from the fixed wear-outtable (step 203), in which fixed entries obtained from previouslyperformed reliability testing have been pre-loaded in the user's system;otherwise the process is ended (step 204). After the frequencyadjustment values have been loaded, the needed adjustments and a time toschedule them may be broadcast to the system or system operator (step205). If the system or system operator approves the plan (step 206),then the system is restarted at the scheduled time with the adjustedoperating frequency (step 207), otherwise a new adjustment plan isformulated and broadcasted. After the system is successfully restartedwith the new adjusted operating frequency, the adjustment is logged(step 208).

Adjustment values can be frequencies, which are used to modify thefrequency at which a clock oscillates. Additionally, the adjustmentvalues can be multiplicands used to modify a clock oscillationfrequency. For example, a 1.0 gigaHz (GHz) base clock frequency could bemultiplied by 1.0 (i.e., yielding 1.0 GHz for an operating frequency)for the first five years of the age of the electronic system, then by0.9 (i.e., yielding 0.9 GHz for an operating frequency for the next fiveyears of the age of the electronic system. The adjustment values can beany value suitable for modifying the operating frequency for theelectronic system or electronic components thereof.

In a second exemplary embodiment, a control unit (called a “wear-outclock”) propagates frequency reductions that are updated from externalsources. Entries for a wear-out table may be collected from reliabilitytests run at the laboratory of the company providing the electronicsystem on a similar or identical system, called the test system, to theend-user system that requires frequency adjustments. These results maythen be fed to a wear-out clock 311 of the end-user system, depicted inFIG. 3 (and described in more detail hereafter), via a direct networkinput 331 that connects the end-user system through a communicationnetwork to the company providing the electronic system. Entries for thewear-out table may be generated by the test system or systems only ashort time in advance of their use in the end-user system. The frequencyof the oscillator may be adjusted according to the logic of the flowchart 200 of FIG. 2. Method 200 also describes how to control theoperating frequency of the system receiving periodic maximum frequencyupdates.

In the flow chart 200 of FIG. 2, the current hours of operation (e.g.,dates) are periodically compared to the hours (e.g., dates) listed in awear-out schedule (step 201), which has, for instance, an adjustment logand a wear-out table. A frequency adjustment is needed (step 202) whenthe current date exceeds the next incremental date entry, defined as thedate entry in a wear-out table that immediately follows the date entrypresently stored in the adjustment log. If a frequency adjustment isneeded, frequency adjustment values are loaded from a transient wear-outtable (step 203), in which entries can be generated just in time fortheir use in the user's system; otherwise the process is ended (step204). After the frequency adjustment values have been loaded, the neededadjustments and a time to schedule them may be broadcast to the systemor system operator (step 205). If the system or system operator approvesthe plan (step 206), then the system is restarted at the scheduled timewith the new adjusted frequency (step 207), otherwise a new adjustmentplan is formulated and broadcasted. After the system is successfullyrestarted, the frequency adjustment is logged (step 208).

It is also possible to assess the performance of the electronic systemwhile it is in use. Performance parameters in this example can includestatistics about performance, such as prior operating frequencies,temperature, and supply voltage. The performance parameters can then beused to adjust operating frequency of the electronic system orelectronic components of the electronic system. The performance may notonly be gauged through operating frequency but may also be assessedthrough performance metrics such as operations per second, throughput,error rate and the like. It is additionally possible to monitor,indirectly or directly, actual maximum frequency of an electronic systemor its components while its is operating.

A synchronously-clocked computer system 300, depicted in FIG. 3, has (a)various electronic components that are synchronous logic chips in thisexample, such as a memory 314, a processor 315, and a digital signalprocessor (DSP) 316, which exchange information among themselves and theoutside world through data busses (not shown), and (b) clock generationcircuits 317, parts of which may reside on the various system logicchips 314, 315, 316 or other dedicated chips. It should also be notedthat the “logic chips” may be integrated into one or more integratedcircuits. Each logic chip receives a system clock, “System Clk,”developed within and broadcast from the clock generation circuits 317.An oscillator 310 residing within the clock generation circuits 317generates the fundamental clock frequency that is boosted to variousdesired frequencies by frequency multipliers 312, 313. Frequencymultipliers 312, 313 multiply the fundamental frequency of theoscillator 310 by N and M, respectively, where N and M may be integersequal to or greater than one. Interconnects 318, 319 distribute theboosted frequencies to the various system electronic components, whichin this example are logic chips 314, 315, 316. The boosted frequenciescarried over interconnects 318, 319 are operating frequencies.

Via interconnect 322, a wear-out clock 311 adjusts the frequency of theoscillator according, for instance, to the logic of the flow chart ofFIG. 2. Moreover, via interconnect 321, the wear-out clock 311 cantrigger an interrupt within the processor 315 to broadcast theadjustment plan as described with respect to step 205 of the flow chart200 of FIG. 2. Input from the system or system administrators can be fedback to the wear-out clock 311 by another interconnect (not shown) orthrough the processor 315. In summary, the wear-out clock 311 regulatesthe frequency of a synchronously clocked computer system 300 byadjusting the operating frequencies to maximize the performance of thesystem's aging components, memory 314, processor 315, and DSP 316. Itshould be noted that the wear-out clock 311 can also contain a processorand memory (not shown). The processor implements method 200 and thememory is used to store the instructions to cause the processor toimplement method 200, along with storing any associated wear-out tablesor other information needed during implementation of method 200.

In this example, a wear-out table 330, such as that shown in FIG. 1B, isshown in memory 314. The wear-out table 330 may also be stored inwear-out clock 311 and may be received via direct network input 331 orthrough another network connection (not shown). Furthermore, thewear-out table 330 may be programmed from the factory with particularinformation, but new information may be received over the direct networkinput 331 or other network input (not shown). The ambient temperature333 may also be used to adjust frequency of the computer system 300 orcomponents thereon. Higher ambient temperature 333, over sufficienttime, has the effect of causing faster wear-out, and the wear-out clock311 can take the higher ambient temperature 333 into account whendetermining what the operating frequency of the computer system 300should be. Ambient temperature is another example of a performanceparameter.

Exemplary embodiments of the present invention described herein may beimplemented as an article of manufacture comprising a machine-readablemedium, as part of memory 314 for example, containing one or moreprograms that when executed implement embodiments of the presentinvention. For instance, the machine-readable medium may contain aprogram configured to perform steps in order to program or modify thewear-out clock 311. The machine-readable medium may be, for instance, arecordable medium such as a hard drive, an optical or magnetic disk, anelectronic memory, or other storage device.

In a third exemplary embodiment, age-monitoring circuits continuouslymonitor performance parameters of an electronic system (such as circuitswitching speed or frequency) for a performance control unit withinwhich the age of the system may be established and through which acorresponding maximum operating frequency performance may be adjusted toaccommodate the effects of aging. The method 400 depicted in FIG. 4describes how the performance control unit 534, for instance, of FIG. 5adjusts frequency performance over the lifetime of a system. In the flowchart 400 of FIG. 4, the steps include monitoring the frequencypotential of a system (step 401), assessing whether or not an adjustmentto its operating frequency is needed (step 402), exiting the flow chartif no adjustment is needed (step 403), and, if an adjustment is needed,restarting system with adjusted performance (step 404), and loggingadjusted performance (step 405). Generally, after a period of time,method 400 will return to step (step 401). The decision (step 402) toreduce the operating frequency of the system is based on whether or notthe system performance has deteriorated to the level where it has littleor no guard-band left in operating performance. If performance hassubstantially deteriorated, the operating frequency of the system isreduced. To ensure functionality at all times, the operating frequencyshould be kept slightly below the performance potential. FIG. 5illustrates an example of how the operating frequency of the electronicsystem, or electronic components thereof, can be changed. For the thirdexemplary embodiment, the feedback circuits 530 are age-monitoringcircuits.

In FIG. 5, a synchronously-clocked computer system 500 with feedback has(a) various electronic components that are synchronous logic chips, suchas a memory 514, a processor 515, and a DSP 516, which exchangeinformation among themselves and the outside world through data busses(not shown), (b) clock generation circuits 517, parts of which mayreside on the synchronous logic chips 514, 515, 516 or other dedicatedchips, and (c) feedback circuits 530, which also may reside on thesynchronous logic chips 514, 515, 516. It should be noted that the logicchips can be integrated into one or more integrated circuits. Each logicchip receives a system clock, “System Clk,” developed within andbroadcast from the clock generation circuits 517. An oscillator 510residing within the clock generation circuits 517 generates afundamental clock frequency that is boosted to various desired operatingfrequencies by frequency multipliers 512, 513. Frequency multipliers512, 513 multiply the fundamental frequency of the oscillator 510 by Nand M, respectively, where N and M may be integers equal to or greaterthan one. Interconnects 518, 519 distribute the boosted frequencies(i.e., the operating frequencies) to the various electronic components,which in this example are synchronous logic chips 514, 515, 516.

Via an interconnect 522, a performance control logic unit 534 adjuststhe operating frequency of the oscillator 510. After gatheringperformance parameters, such as circuit switching speed or oscillatorfrequency, from the feedback circuits located on the synchronous logicchips 514, 515, and 516, the performance control unit 534 decideswhether the operating performance of the system requires adjustment,according to the procedure set forth in the flow chart 400 of FIG. 4 orthe procedure set forth in the flow chart 600 of FIG. 6. The performancecontrol unit 534 regulates the frequency of a synchronously clockedcomputer system 500 by adjusting the frequency to maximize theperformance of its aging components while maintaining theirfunctionality. It should be noted that the performance control unit 534may also include a processor and memory (not shown). In this case, theprocessor would implement method 400 and the memory would store theinstructions to cause the processor to implement method 400 and wouldalso store any associated data from the feedback circuits 530 or otherinformation needed during implementation of method 500.

Age-monitoring circuits—feedback circuits 530 for the exemplary thirdembodiment—are known in the art of analog electronics. Aging statisticsmay be obtained by comparing a continuously operating test circuit, theaging circuit, with a test circuit that is enabled only for thecomparison, the new circuit. Such aging statistics could be extracted asthe time difference between two signals, one that traverses an agedinverter chain and another that traverses a new inverter chain.

In a fourth exemplary embodiment, the frequency of the system may beadjusted over the system lifetime by detecting and reacting to systemfailures. Error detecting circuits are inserted in system components ina fashion similar to the age monitoring circuits described previouslywith respect to the third exemplary embodiment, the primary differencebetween fourth and third embodiments being that error detecting circuitsassess the logic circuits directly whereas the age-monitoring circuitsrun independent tests to gauge performance. In the fourth embodiment,the feedback circuits 530 are more narrowly defined as error detectingcircuits that are suitable for detecting errors in the logic circuits(as opposed, for instance, to detecting errors caused by software).

In addition, a system 500 according to the fourth embodiment may bedesigned to include elements to correct errors, or to back up theprogram flow to a state previous to the detected error and re-executethe instructions. Hence even though the third and fourth embodimentsemploy the same feedback apparatus (depicted in FIG. 5), a new method600, depicted in FIG. 6, is devised to handle the error or errorsdetected prior to restarting the system being restarted with theadjusted frequency.

When an error is detected by one of the error detecting circuits, thesystem enters an error diagnostic mode of operation (step 605). Ingeneral, the diagnostic operating mode makes a decision as to whether achange in operating frequency is needed (step 610), and if so, resetsthe system operating frequency and logs the event as describedpreviously. The operations of the diagnostic operating mode aregenerally pre-defined, along with the other operating characteristics ofthe system. These operations may include procedures developed fromprevious experience with system reliability and may use pre-collecteddata from extended life testing, or they may include dynamic tests anddecisions based on results of these tests.

An example of a possible diagnosis of a system error is to first resetthe system to a state before the detected error occurred, and re-executethe instructions up to the point where the error was detected (step615). If the error does not occur in this test (step 620=YES), thediagnostic system may log the results of the test and return the systemto normal operation (step 640). If the error does occur in the test(step 620=NO), the diagnostic system may lower the system operatingfrequency (step 625) and re-run the test at the lower operatingfrequency (step 630). When lowering the operating frequency eliminatesthe error (step 633=YES), corrective action is logged, and the system isreturned to normal operating mode at the lower frequency (step 635). Ifthe error is not corrected (step 633=NO), the method continues at step625, where another operating frequency is selected. Method 400 ends instep 640.

Exemplary aspects of the present invention may also be implemented alongwith power saving features. For example, the operating frequency doesnot always have to be near the maximum operating frequency for theelectronic system or its constituent electronic components at aparticular age. Thus in some instances, a lower operating frequencycould be selected to reduce power, while in other instances, whenperformance is required, an operating frequency close to the maximumoperating frequency could be selected according to the techniques ofexemplary aspects of the present invention.

Additionally, it may be possible to use the techniques of exemplaryaspects of the present invention to raise operating frequency in theshort term. For instance, if ambient temperature remains low as thesystem runs, operating frequency may be able to be raised based on therelatively low ambient temperature.

It is to be understood that the embodiments and variations shown anddescribed herein are merely illustrative of the principles of thisinvention and that various modifications may be implemented by thoseskilled in the art without departing from the scope and spirit of theinvention.

1. I method of frequency modification for one or more electroniccomponents in an electronic system, the method comprising the steps of:determining, at a particular age of the electronic system, one or moreperformance parameters for the electronic system, the one or moreperformance parameters correlated with maximum operating frequency ofone or more electronic components of the electronic system for theparticular age of the electronic system; and adjusting an operatingfrequency of the one or more electronic components from the electronicsystem in accordance with the one or more performance parameters.
 2. Themethod of claim 1, wherein the step of adjusting adjusts the operatingfrequency to an adjusted operating frequency, and wherein the adjustedoperating frequency is less than or equal to the maximum operatingfrequency of the one or more electronic components for the particularage of the system.
 3. The method of claim 1, wherein a given one of theone or more performance parameters can be converted to a selectedoperating frequency to be used in the step of adjusting.
 4. The methodof claim 3, wherein the given performance parameter comprises amultiplicand used to convert a base frequency to the selected operatingfrequency to be used in the step of adjusting.
 5. The method of claim 1,wherein the step of determining a performance parameter furthercomprises the steps of determining whether the particular age of theelectronic system is a predetermined age, and determining an operatingfrequency from the one or more performance parameters when theparticular age is the given age.
 6. The method of claim 5, wherein agiven one of the one or more performance parameters comprises apredetermined operating frequency to be used in the steps of determiningand adjusting.
 7. The method of claim 1, wherein the step ofdetermining, at a particular age of the electronic system, a performanceparameter for the electronic system, further comprises the step ofgathering, at the particular age of the electronic system, performancestatistics from one or more feedback circuits, and determining whetheractual performance of the electronic system should be adjusted by usingthe performance statistics.
 8. The method of claim 7, wherein the stepof gathering, at the particular age of the electronic system,performance statistics from one or more feedback circuits, furthercomprises the step of gathering, at the particular age of the electronicsystem, performance statistics from one or more age-monitoring circuits.9. The method of claim 8, wherein the step of gathering, at theparticular age of the electronic system, performance statistics from oneor more age-monitoring circuits further comprises the step ofdetermining, at the particular age of the electronic system, a givenperformance statistic by comparing speed of an aged circuit with speedof a test circuit that is enabled only for the comparison, wherein theaged circuit has been operated for approximately the particular age. 10.The method of claim 7, wherein the step of gathering, at the particularage of the electronic system, performance statistics from one or morefeedback circuits, further comprises the step of gathering, at theparticular age of the electronic system, performance statistics from oneor more error detecting circuits.
 11. The method of claim 10, wherein:the step of gathering further comprises the step of determining that oneor more errors have occurred; and the step of adjusting an operatingfrequency further comprises the steps of lowering operating frequencyfrom a current operating frequency, beginning execution at a pointbefore the one or more errors occurred, determining if the one or moreerrors reoccur, and if the one or more errors do not reoccur, leavingthe lowered operating frequency as the current operating frequency. 12.The method of claim 11, wherein the step of adjusting further comprises,before the step of lowering operating frequency, the steps of beginningexecution at a point before the one or more errors occurred, determiningif the one or more errors reoccur, and if the one or more errors do notreoccur, leaving current operating frequency alone.
 13. The method ofclaim 1, wherein the one or more performance parameters comprise one ormore of previous operating frequency, ambient temperature, hours ofoperation, and supply voltage.
 14. The method of claim 1, wherein theone or more performance parameters are stored performance parameters andwherein the method further comprises the step performing reliabilitytesting to determine wear-out information comprising the storedperformance parameters.
 15. The method of claim 14, wherein the storedperformance parameters comprise predetermined ages and predeterminedoperating frequencies at corresponding ones of the predetermined ages.16. The method of claim 14, wherein the step of performing reliabilitytesting further comprises the step of determining one or more prioroperating frequencies of the electronic system, one or more ambienttemperatures surrounding the electronic system, and one or more supplyvoltages of the electronic system.
 17. The method of claim 16, furthercomprising the step of providing supply voltage for the electronicsystem that is higher than nominal supply voltage.
 18. The method ofclaim 16, further comprising the step of providing ambient temperaturesurrounding the electronic system that is higher than nominal ambienttemperature.
 19. The method of claim 1, wherein the performanceparameters are received from an external source.
 20. An electronicsystem able to perform frequency modification for electronic components,the electronic system comprising: one or more electronic components; atleast one clock generation circuit coupled to the one or more electroniccomponents and adapted to: determine, at a particular age of theelectronic system, one or more performance parameters for the electronicsystem, the one or more performance parameters correlated with maximumoperating frequency of one or more electronic components of theelectronic system for the particular age of the electronic system; andadjust an operating frequency of the one or more electronic componentsfrom the electronic system in accordance with the one or moreperformance parameters.
 21. The electronic system of claim 20, wherein:the performance parameters comprise a plurality of predetermined agesand a corresponding plurality of predetermined operating frequencies;the at least one clock generation circuit comprises a wear-out clock;the wear-out clock is adapted to determine, at a particular age of theelectronic system, one or more of the predetermined ages and todetermine whether a current age of the electronic system corresponds toa given one of the predetermined ages; and the wear-out clock is furtheradapted to adjust operating frequency of the one or more electroniccomponents by adjusting a current operating frequency of the one or moreelectronic components to a predetermined operating frequencycorresponding to the given predetermined age.
 22. The electronic systemof claim 21, wherein the wear-out clock is further adapted to retrievethe predetermined ages and corresponding predetermined operatingfrequencies from a source external to the wear-out clock.
 23. Theelectronic system of claim 20, wherein the at least one clock generationcircuit further comprises a performance control unit.
 24. The electronicsystem of claim 23, further comprising one or more feedback circuits inthe one or more electronic components, the one or more feedback circuitscoupled to the performance control unit.
 25. The electronic system ofclaim 24, wherein a given one of the one or more performance parameterscomprises one or more performance statistics, wherein a given one of thefeedback circuits comprises an age-monitoring circuit comprising an agedcircuit and a new circuit, wherein the performance control unit isadapted to enable the new circuit only during a comparison between theaged and new circuits and to determine the one or more performancestatistics from the comparison, wherein the aged circuit has beenoperated for approximately the particular age.
 26. The electronic systemof claim 24, wherein: a given one of the one or more performanceparameters comprises one or more performance statistics; a given one ofthe feedback circuits comprises an error detecting circuit, the errordetecting circuit adapted to determine if an error occurs, wherein theone or more performance statistics indicate than an error has occurred;the performance control unit is further adapted to receive the one ormore performance statistics, indicating that one or more errors haveoccurred, from the error detection circuit, to lower operating frequencyfrom a current operating frequency, to cause execution to begin at apoint before the one or more errors occurred, to determine if the errorreoccurs, and if the error does not reoccur, to leave the loweredoperating frequency as the current operating frequency.
 27. Theelectronic system of claim 20, wherein the at least one clock generationcircuit further comprises an oscillator and one or more frequencymultipliers, the oscillator having an output, each of the one or more ofthe frequency multipliers having an input and output, the output of theoscillator coupled to an input of each of the one or more frequencymultipliers, a given one of the one or more electronic componentscoupled to an output of a given one of the one or more frequencymultipliers, and wherein the at least one clock generation circuit isfurther adapted to create an adjusted operating frequency for the givenelectronic component by adjusting one or more of the following:operating frequency of the oscillator and a multiplicand used in thegiven frequency multiplier.
 28. An article of manufacture for performingfrequency modification for electronic components, the article ofmanufacture comprising: a computer readable medium containing one ormore programs which when executed implement the steps of: determining,at a particular age of the electronic system, one or more performanceparameters for the electronic system, the one or more performanceparameters correlated with maximum operating frequency of one or moreelectronic components of the electronic system for the particular age ofthe electronic system; and adjusting an operating frequency of the oneor more electronic components from the electronic system in accordancewith the one or more performance parameters.